Sterchi, Yanik

Sterchi, Yanik


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  • Publikation
    Why stop after 20 minutes? Breaks and target prevalence in a 60-minute X-ray baggage screening task
    (Elsevier, 03/2020) Buser, Daniela; Sterchi, Yanik; Schwaninger, Adrian [in: International Journal of Industrial Ergonomics]
    Current EU regulation restricts continuously reviewing X-ray images of passenger baggage to 20-min duration as a precautionary measure to prevent performance decrements in airport security officers (screeners). However, this 20-min limit is not based on clear empirical evidence on how well screeners can sustain their performance over time. Our study tested screeners in a 60-min simulated X-ray cabin baggage screening task. One group took 10-min breaks after 20 min of screening; the other group worked without breaks. We found no decrease in performance over 60 min in either group. Breaks did not affect performance, but they did reduce the amount of subjective distress. By varying target prevalence, we found that da with a slope of about 0.6 is a more valid measure of detection performance than d’. Target prevalence caused a criterion shift. Our results provide a basis for conducting field studies of prolonged screening durations, and open the discussion on whether more flexible break policies and work schedules should be considered.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Detection measures for visual inspection of X-ray images of passenger baggage
    (Springer, 2019) Sterchi, Yanik; Hättenschwiler, Nicole; Schwaninger, Adrian [in: Attention, Perception, & Psychophysics]
    In visual inspection tasks, such as airport security and medical screening, researchers often use the detection measures d' or A' to analyze detection performance independent of response ten-dency. However, recent studies that manipulated the frequency of targets (target prevalence) indicate that da with a slope parameter of 0.6 is more valid for such tasks than d' or A'. We in-vestigated the validity of detection measures (d', A', and da) using two experiments. In the first experiment, 31 security officers completed a simulated X-ray baggage inspection task while re-sponse tendency was manipulated directly through instruction. The participants knew half of the prohibited items used in the study from training, whereas the other half were novel, thereby es-tablishing two levels of task difficulty. The results demonstrated that for both levels, d' and A' de-creased when the criterion became more liberal, whereas da with a slope parameter of 0.6 re-mained constant. Eye-tracking data indicated that manipulating response tendency affected the decision component of the inspection task rather than search errors. In the second experiment, 124 security officers completed another simulated X-ray baggage inspection task. Receiver op-erating characteristic (ROC) curves based on confidence ratings provided further support for da, and the estimated slope parameter was 0.5. Consistent with previous findings, our results imply that d' and A' are not valid measures of detection performance in X-ray image inspection. We recommend always calculating da with a slope parameter of 0.5 in addition to d' to avoid poten-tially wrong conclusions if ROC curves are not available.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Traditional visual search vs. X-ray image inspection in students and professionals: Are the same visual-cognitive abilities needed?
    (Frontiers, 2019) Hättenschwiler, Nicole; Merks, Sarah; Sterchi, Yanik; Schwaninger, Adrian [in: Frontiers in Psychology]
    The act of looking for targets amongst an array of distractors is a cognitive task that has been studied extensively over many decades and has many real-world applications. Research shows that specific visual-cognitive abilities are needed to efficiently and effectively locate a target among distractors. It is, however, not always clear whether the results from traditional, simplified visual search tasks conducted by students will extrapolate to an applied inspection tasks in which professionals search for targets that are more complex, ambiguous, and less salient. More concretely, there are several potential challenges when interpreting traditional visual search results in terms of their implications for the X-ray image inspection task. In this study, we tested whether a theoretical intelligence model with known facets of visual-cognitive abilities (visual processing Gv, short-term memory Gsm, and processing speed Gs) can predict performance in both a traditional visual search task and an X-ray image inspection task in both students and professionals. Results showed that visual search ability as measured with a traditional visual search task is not comparable to an applied X-ray image inspection task. Even though both tasks require aspects of the same visual-cognitive abilities, the overlap between the tasks was small. We concluded that different aspects of visual-cognitive abilities predict performance on the measured tasks. Furthermore, although our tested populations were comparable in terms of performance predictors based on visual-cognitive abilities, professionals outperformed students on an applied X-ray image inspection task. Hence, inferences from our research questions have to be treated with caution, because the comparability of the two populations depends on the task.
    01A - Beitrag in wissenschaftlicher Zeitschrift